A droplet actuator typically includes one or more substrates configured to form a surface or gap for conducting droplet operations. The one or more substrates establish a droplet operations surface or gap for conducting droplet operations and may also include electrodes arranged to conduct the droplet operations. The droplet operations substrate or the gap between the substrates may be coated or filled with a filler fluid that is immiscible with the liquid that forms the droplets. Sometimes the substrates of droplet actuators are not suitably planar and/or parallel when assembled, which may result, for example, in non-uniform gap height. Therefore, there is a need for mechanisms to ensure that the top and bottom substrates of a droplet actuator are planar and parallel when in use.
The invention provides an apparatus, including a microfluidics system. The system may have an insertion slot for insertion of a droplet actuator. The system may have a bottom plate against which the droplet actuator would slide when inserting the droplet actuator into the insertion slot. The system may have means for forcing a substrate in the droplet actuator parallel to the bottom plate. In this manner, warpage in the substrate is corrected. In some cases, the means for forcing the substrate comprises means for mechanically forcing the substrate against the bottom plate of the microfluidics system. In some cases, the means for forcing the substrate comprises means for mechanically forcing the droplet actuator against the bottom plate of the microfluidics system. In some cases, the means for forcing the substrate comprises at least one pressure point that forces the substrate against the bottom plate. In some cases, the means for forcing the substrate comprises at least one pressure point that forces the droplet actuator against the bottom plate. In some cases, the means for forcing the substrate comprises at least one spring that forces the substrate against the bottom plate. In some cases, the means for forcing the substrate comprises a spring mechanism applying a force to a top substrate in the droplet actuator.
The invention provides an apparatus, including a droplet actuator for insertion into an insertion slot of a microfluidics system, a top substrate and a bottom substrate defining a gap in the droplet actuator, droplet operations electrodes in the bottom surface for transporting a droplet along the gap, and means for seating a force applied to the top substrate that corrects warpage in the bottom substrate. In some cases, the means for seating the force comprises at least one detent in a top surface of the top substrate. In some cases, the apparatus includes a gap setting feature aligned with the at least one detent, the gap setting feature establishing a minimum height of the gap between the top substrate and the bottom substrate. In some cases, the apparatus includes a gap setting feature that establishes a minimum height of the gap between the top substrate and the bottom substrate. In some cases, the apparatus includes a gap setting feature protruding from the top substrate that establishes a minimum height of the gap between the top substrate and the bottom substrate. In some cases, the apparatus includes a ramped edge in the droplet actuator to reduce friction during the insertion into the insertion slot of the microfluidics system. In some cases, the apparatus includes a ramp proximate a leading edge of the top substrate to reduce friction during the insertion into the insertion slot of the microfluidics system. In some cases, the means for seating the force comprises multiple detents in a top surface of the top substrate. In some cases, the apparatus includes multiple ramped surfaces in the top substrate of the droplet actuator, each ramped surface aligned to lead a corresponding one of the multiple detents, the multiple ramped surfaces reducing friction during the insertion of the droplet actuator into the insertion slot of the microfluidics system.
The invention provides a method, including receiving a droplet actuator in an insertion slot of a microfluidics system, and forcing a substrate in the droplet actuator parallel to a plate in the microfluidics system, wherein warpage in the substrate is corrected. In certain embodiments, the method includes depressing a spring plunger as the droplet actuator is inserted into the insertion slot. In certain embodiments, the method includes seating a tip of the spring plunger as the droplet actuator is inserted into the insertion slot. In certain embodiments, the method includes dimpling a top surface of the substrate. In certain embodiments, the method includes maintaining a minimum height of a droplet operations gap in the droplet actuator. In certain embodiments, the method includes deforming the substrate parallel to the plate in the microfluidics system.
The invention provides an apparatus including a microfluidics system having a droplet actuator inserted into an insertion slot, a bottom plate against which the droplet actuator slides as the droplet actuator inserts into the insertion slot, a spring plunger applying a force to a substrate of the droplet actuator, and a detent in the substrate of the droplet actuator into which a tip of the spring plunger seats, wherein the spring plunger forces the substrate parallel to the bottom plate to correct warpage. In some cases, the apparatus includes a gap setting feature establishing a minimum height of a droplet operations gap in the droplet actuator. In some cases, the apparatus includes a gap setting feature protruding from the substrate that establishes a minimum height of a droplet operations gap in the droplet actuator. In some cases, the apparatus includes a ramped edge along the droplet actuator to reduce friction during the insertion into the insertion slot of the microfluidics system. In some cases, the apparatus includes a ramp proximate a leading edge of the substrate to reduce friction during the insertion into the insertion slot of the microfluidics system. In some cases, the apparatus includes multiple detents in a top surface of the substrate. In some cases, the apparatus includes multiple spring plungers applying multiple forces to the substrate of the droplet actuator, and multiple detents in a top surface of the substrate of the droplet actuator. In certain embodiments, each tip of a corresponding one of the multiple spring plungers seats into a corresponding one of the multiple detents. In some cases, the apparatus includes multiple ramped surfaces in the substrate of the droplet actuator, each one of the multiple ramped surfaces aligned to lead the corresponding one of the multiple detents, each of the multiple ramped surfaces reducing friction during the insertion of the droplet actuator into the insertion slot of the microfluidics system.